Oil Pressure Problem?
 

What would cause the oil pressure to drop like this? Constant cruising speed 2400rpm. It drops slowly about 10 psi and sometimes very quickly. But it always comes back up. Running VR1 20w50 oil and the mechanical gauge is plumed at filter housing. Here is the video:
https://www.youtube.com/watch?v=Q9fI4O6kN_8

Does it do in higher rpms? Mybe the pickup is coming loose? Change gage to see if the gage is the problem. Could it be loose at the back of the gage?

Accelerating it seems good. At idle it does the same thing.

I would change the gage just to rule it in or out.

Once oil is hot(oil temp 180°+), pressure @ idle in neutral(1400rpm) is 20psi and in gear (1000rpm) 10psi. Is this an indicator of anything?

I guess it could be but i dont see anything bad at this point. Id change the gage and go from there. See what happens .

Do you still have the Pontiac oil filter housing unit installed on the block? If so I would remove it and check the bypass on it. You can always stretch the spring inside it a bit to hold the bypass close. It's held on with a tiny screw to the housing. Put a dab of blue locktite on the screw when installing. Check the disk and sometimes the metal tab is bent out allowing oil to bypass.

I had a check valve in the oil pump get stuck open when a piece of junk got underneath it.

When I first fired the engine up cold, the oil pressure would rise very slow, but steady up to about 60 PSI. As the engine got warm, the oil pressure would begin to drop closer to 50PSI. The pressure would also waiver, kinda like yours. I knew I had a problem, but just did not want to pull the engine until oil pressure quit on me. So I added heavier oil - which raised pressure, but it still had issues. The pressure began to sink again, so in when some nice thick STP. Pressure went up a little again and was tolerable. Pressure was OK with RPM's and would only hit 40 PSI, but not good at idle, so up went my idle speed to 1,200 RPM ( it was a manual car) and it would hit about 12 PSI.

Finally after 7 years of this, one day I fired it up and the oil pressure was 0. My excuse to do a fresh rebuild on a 455CI I have. Pulled down the 400CI to find the a piece of trash stuck under the check ball in the oil pump so it would not close, and all the bearings were wiped out showing copper. Pics of the rod bearings are below and the mains didn't look healthy. Just a little extra clearances for high RPM racing, right?

Like suggested, change the gauge out first before assuming any big problems.

Pull the motor now before you ventilate the block with Broken Rods!
You have a unseated check ball issue and may have all ready caused Bearing damage.

I just had a little piece of debris in my check ball. It lowered the idle pressure but never went up and down like yours..

Id take about the oil filter housing, the bypass in it might be doing wierd things. It's easy to do and worth a try before going through all the trouble of pulling the engine.

Im going to swap the gauge with another mechanical. If that doesn't do the trick Ill check out the filter housing bypass. What about plugging the bypass in filter housing? The motor has a solid roller cam and driven on the street a bit and will be taken to the track. Is the sole purpose of it to open when the oil filter is totally clogged?

Never having a roller cam, you stated you have a solid roller. From my reading, with a solid roller the lifter bores need to have restrictors installed in the oiling-to-lifter holes or too much oil will flow, ie act like a big leak - might this be the problem? Were restrictors put in with your engine?

The roller guys can chime in as I have no hands-on experience, just what I have read in several publications.

I have mine plugged . No problems. I think that you're on the right path. If the gage dont change anything then id check the bypass like suggested.

I had a unseated check ball once and the pressure was irratic dependant on the oil temp , but the the thing it would constantly do once the oil temp got up to 180 was the from idle the oil pressure would rise about 4 times slower when accelerating then it normally would.

You can forget about the oil filter adapter bypass causing the problem. You could totally remove the bypass flap and spring and the only thing you might see is a little increase in pressure since most of the oil would be bypassing the filter medium. The adapter bypass only determines where the oil goes inside the adapter - whether through the filter or around the filter. Now the bypass on the pump does cause problems when a chunk of crap gets lodged, but the recovery of pressure and the repeatability of the pressure drop almost seems like a lack of oil to the pump - either by low oil, pickup fell off, or possibly cavitation.

I tried a different gauge and got the same results. Could the location of my pressure gauge on the filter housing cause the bad reading? I am using a Purolator filter: http://oilfilterdata.com/index.php?v...o&model=L25288 Where is another spot to take oil pressure readings?

Did you check the oil filter housing ?

You can also check oil pressure on top of block by the distributor.

Can you post a pic of where your pulling pressure from on the oil filter housing ?

I am going to take a look and see. Lust4speeds comment about the bypass makes sense. But I'm wondering if maybe there's something funky about the filter I'm using and the gauge line being right off of it. I am pulling from right above the oil filter on the housing.

If memory serves me correctly the port on the oil filter housing monitors the oil pump and top of block is after oil filter, which if that’s the case, problem points to oil pump. I’ll have to check a oil filter housing again.

Put a wix filter oil while your at it.

I would pull that engine down ASAP. I had a buddy years ago had a issue like that, pickup was laying in the bottom of the pan. It still ran but the bearings looked like garbage.

Correct, thats way taking pressure by dist is usually a few lbs lower (its after the filter).

Did he still have good oil pressure at idle?

https://www.youtube.com/watch?v=JNfG...ature=youtu.be

Check this out. This is in neutral at idle. It almost seems like the same timing intervals of the drop are the same when at cruise.

Can't say for sure, long time ago.
With my engine about 15 years ago I went from a Canton pan to s stock one and put a different 60lb pump with stock pickup on.
Took it to the track and the oil pressure would go down to 10lbs at idle. Slowly climb with RPM. I shut it off, pushed it back on the trailer, pushed it off the trailer and into the garage. Pulled the engine that nite. Took the pump that had the Canton pickup on it and switched it to a stock style pickup. I knew that pump worked flawlessly.
That is after pulling some main caps to check bearing condition. I still have the pump I removed that nite. I bet it has something stuck around the check ball. Its a pump I had on the car my senior year in High School, only ran for a year. But I don,t trust it. Might be fine with cleaning but its not going back in any of my engines.
Don't mess with this, pull the engine. At this point I bet you have some bearing damage.

Stop procrastinating and yank the motor while it's still rebuildable!

Many moons ago I had a stock 455 that had low oil pressure for just 3 days and then fortunately the 4th day at only 30 mph it went from dead quite to really loud rod hammering in 15 seconds!
I was lucky and shut it down and saved everything, if I was on the highway and that took place up at another 1000 rpm or so I am sure that rod would have ventilated the block before I was able to shut it down!

Hello All,
Has anybody ever considered removing the oil filter adapter completely and making a cap for the block. Then use an oil primer drive for the distributor to cause the pump to go over relief this would force a large amount of oil through the relief and my clear any debris/junk in the seat of the relief? Seems like I read a GM service note about this somewhere?

Vince

Bleed the air out of the line to the gauge..

Change the oil to 5-30 Mobil 1 synthetic..

Add a quart of Shaler Rislone to the new oil...

I've seen the picture of this from a service manual - probably here on PY
 

I don't think you would need to use a priming tool, though.

Just pull the coil wire and crank for a few seconds. Maybe repeat a few times.

Couldn't hurt things any more than they are probably already hurt.

Good luck!

I was just thinking using the primmer tool would be less wear and tear on the distributor roll pin.
Vince

What do you think adding Rislone to the oil will accomplish especially if his pumps check ball his being held open ?

add an extra quart of oil and see if the problem goes away if it does its pick up related if it doesn't then look at the pump . Idoubt that the filter housing is your problem unless your filter is completely plugged.

What is 'typical' oil pressure, hot, at idle and cruise rpm?

Its been a while but I finally got some time to pull the motor down. The rod bearings were all worn to copper. No.2 main bearing was completely spun, the other mains pretty worn. The most glaring problem as of now as a possible culprit, is my flexplate bolt heads colliding with the torque converter. Anyone ever see the aftermath of that? I have not measured the end play yet for thrust bearing, and I still need to open up oil pump. I cant believe this thing lived as long as it did. I was planning on taking it to the track for the first time this summer and wanted to make sure there were no issues. Good thing I checked.

If your flexplate bolts were hitting the converter, how were you able to bolt the converter to the flexplate? The distance from the flexplate to the converter mounting pads is only 1/8" to 3/16" max. when converter is fully seated in the transmission. Anymore than 3/16" and shims are required between the flexplate and converter. There would have been a space when you went to bolt converter to flexplate. In other words, when you pulled converter up to the flexplate, the converter should have hit the head bolts before the converter mounting pads hit the flexplate.
I can see the witness marks on the converter pic.
One measurement you can do is with the torque converter fully seated in the transmission, measure from the face of the bellhousing to the converter mounting pads. Should be min. 1". Some say 1-1/8"

Another thing to check is that the hub of the converter fits into the crank. Also, next time your putting everything back together, you can spin the converter before bolting it to the flaxplate to check for any binding. Doesn't hurt to put a bit of grease on the hub of the converter before bolting it to the flexplate. The Flexplate does flex so the 1/8" to 3/16" is so the converter can move back and forth.

Thing is, the by pass valve is your safety for a problem with the oil filter. Eliminating it does nothing to help the longevity of the engine. Starting the engine cold, can crush the filter media hydraulically. I can't for the life of me figure out why people plug the relief off.

If you want better filtering, a by pass filter is the way to get better filtering, not plugging the by pass valve. Pontiac is one of the engines that does not have a by pass valve internal to the filter. You have no safety valve when the by pass is plugged. The oil enters on the outside of the filter, passes through the media, and returns through the center to the internal engine parts.

Over pressuring the canister, can split the canister housing, force the O ring to leak, and crush the media. If the media ruptures, all the filtered dirt is free to pass right into the bearings. You have to ask yourself, what did I save by eliminating the by pass valve? The answer is you didn't save anything, you can ruin the whole engine if the media ruptures, and dumps all the filter contents directly into the engine. The scary thing is, you'll never know the media ruptured unless you dissect every filter by cutting it open, pulling all the pleats, and carefully examining the media. If you do find a compromised filter, the damage is already done.

If you change the filter, and toss the filter, the way you may find out is when the bearings fail, for no apparent reason. The idea for removing the by pass valve is to make every bit of oil flow through the filter. The problem with that theory is, a full flow filter filters down to 40 microns. The dirt that grinds up engine parts is small enough that it passes through the media anyway. 10 microns is the particulate size that can fit into the tight tolerances and grind away at the internal engine parts. The 40 micron size doesn't fit between the bearings and crankshaft, it can't fit in the tight spaces.

If you spend time researching, most engine builders (not every one) dismiss blocking the by pass valve as unnecessary. I've never blocked it in any engine I've ever built. If you want clean oil, a full flow filter will never provide it, the design is to filter out big pieces of dirt. If a full flow filter kept your oil clean, you wouldn't have to keep changing oil to get the small particulate out of the oil.

If you leave the oil in the engine, the small particles will keep getting denser. Everyone knows what happens if you don't change oil with a full flow filter system, sludge and engine wear ensues. Sludge is made up of the fine matter that flows through the full flow filter unimpeded.

Two ways to remove the fine stuff, flush the engine with fresh oil continually, or get a filter that removes it first pass. I use the second method to catch the fine matter first pass, rather than wait until I change oil to remove it from the engine.

One other thing, putting multiple full flow filters does decrease pressure loss across the filters, but it still doesn't remove the harmful matter that passes through a full flow filter.

:focus:

You have it backwards. Port by distributor is directly from the pump port on filter housing is after filter.

The port by the distributor is directly from the pump.

Im 98% sure the port by dist is after the filter, not directly from pump.

Pump flow goes directly out the bottom port at oil filter. Then comes back in engine at top port, goes across the top of #5 main to the vertical passage by distributor. From there it goes down and forward to the left side lifter galley, feeding all the mains. Feed from #1 main comes back up to right side lifter galley.

Eric

Let me start by saying I did not build this motor. I have owned the car for 3 years and the previous owner (not builder) had no business owning a car like this. It was very neglected. This is the first time I have had it apart so I have the same questions as all of you. The bypass on the filter housing was plugged.

Drain oil, ck for shiny particles.

Has anyone ever seen mains on a crank with 'chamfers' this big?

I never put restrictors at the lifters for a street car.Tom

Note my comments in post #8 & #11 here:

https://forums.maxperformanceinc.com...=oil+pump+dyno


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